Electric chain saw sharpening machine

ABSTRACT

The present invention relates to an electric sharpening machine for chain saws capable of correctly sharpening the teeth of every kind of saw; this system according to the invention allows to rotate all the upper group with the motor and the grinding wheel, to balance the chain stop situated on the vice and, in addition, to turn the saw of 180°; in this way it is possible to let the abrasive vice sharpening the saw teeth rotate, both in case of left and right teeth, towards the inner part opposite to the position of the operator.

[0001] Electric chain saw sharpening machine with movement of the upper arm and displacement of the chain stop for obtaining a true sharpening of the chain saw right and left teeth.

[0002] Preliminary statement: in order to better understand how to use the sharpening machine and the features of the present invention a short description of the chain saws is necessary. Every saw (FIG. 2) is formed by a series of driving chains with a thickness variable from 1.1 mm to 2.0 mm, but some special chains reach a thickness of 3.1 mm. These chains are joined each other by a couple of jointing or connection chains fixed by means of rivets allowing the articulation of the chain (FIG. 3). In the standard saw the driving chains are connected to a connection chain and this one to a chain with a special form having a sharp which is always turned towards the inside of the saw; this sharp will be named right or left (FIGS. 2 and 3). The sharp or tooth has a profile with an upper cutting angle and a lateral cutting angle (FIG. 4), these angles have to be perfectly sharpened, with the true and same angle either in case of right or left, since, only in this way, during the cutting, the teeth come into the wood and they remove the shaving from the log in a perfectly identical way and the saw works without excessive stress. In order to reinforce the hardness of these teeth, the manufacturers coat with a chrome layer the external surfaces to grant a better resistance of the metal against the cutting stress on the wood.

[0003] By the electric sharpening the grinding wheel overheats the chromate cutting part of the tooth and, because of the rubbing, some little metal feather edges and some little irregularities of the lateral and upper cutting angle are formed, but only on the internal part with respect to the entry part of the grinding wheel. That external part (which is the first one to be touched) remains perfectly regular and well sharpened.

[0004] Up to some years ago, the electric sharpening machines for chain saws were expected to have a double rotation of the motor and, consequently, of the grinding wheel connected to the motor in order to get a rotation for the removing of the material from the tooth; this removing having to be always from the external part towards the inner part (FIG. 5, drawing 1) both in case of right and left teeth. If the feather edges and the irregularities are turned towards the inside of the tooth, the external cutting part maintains the chrome layer and it presents a perfect cutting angle.

[0005] When the saw to cut the wood is going to be used, the saw and the chain saw will work better, with less stress and the cutting will be more accurate.

[0006] The introduction of the CE rule referring to the operator safety (89/39 No. 73/23 No. 89/336 and following integration, updating and amendments) forbids that the material removed from the tooth of the saw and the sparks can be turned towards the operator. Of course, in case of grinding wheel breaking as well as in case of removing of metal particles from the saw the operator could be seriously hurt.

[0007] On the other hand the operator, for an accurate sharpening, needs to keep a good visibility on the grinding wheel/tooth contact point of the saw and it results therefore difficult for a manufacturer to place proper protection means. For this reason the present manufacturers have chosen a solution which provides only a rotation direction for the electric motor (and consequently for the grinding wheel connected to the motor); this direction being opposite to the position of the operator. Further to this choice the positions cannot grant anymore to the right and left teeth of a chain saw a perfectly identical sharpening.

[0008] The purposes of the present invention are, therefore, the following:

[0009] 1. to create an electric sharpening machine which assures the maximum safety for the operator and the observance of the European rules in force, allows to sharpen both right and left teeth of a saw by means of a rotation of the grinding wheel always turned from the external part towards the inner part (following the upper and lateral cutting angle of the saw teeth).

[0010] 2. to make this further adjusting easy and able to reduce any waste of time for the operator.

[0011] 3. by the sharpening, to stop the chain between the two yaws by a mechanical system, without any further manual actions by the operator.

[0012] Another feature is the system stopping the chain to be sharpened in the yaws of the vice. By lowering the upper group including the motor and the grinding wheel, the spring B10 is stressed acting the arm B11, which, in its turn, creates a lever on the shaped block B12 able to displace for reaching a pressure on the inner yaw B13 which stops the saw to be sharpened (FIG. 1).

[0013] a) The sharpening machine according to the invention solves the problem concerning the sharpening by an easy and improving way, by solving contemporaneously the points 1 and 2.

[0014] The upper part of the machine (arm A2) and the lower part (base A4) have been realised in order to allow a rotation of the upper part of 80° on the groove A5 situated on the base A4 (FIG. 6). That means that it can be located in all the spaces included between 40° on the right (corresponding to 50° on the graduated scale A8) and 40° on the left (that is 50° in this direction) (FIG. 7) with respect to the central axis (90°). In order to do this operation it is enough to unscrew the handle A6 situated on the back of the sharpening machine and place it where wished (as the skilled knows this angle must correspond to the lateral cutting angle of the tooth as called by the saw manufacturers, FIG. 4, in order to place the grinding wheel perfectly parallel to the inclination of the tooth). To read the inclination angle of the head A2 or on the graduated scale A20 situated on the front of the machine or on the graduated scale A8 situated on the milled surface of the back part (FIGS. 7, 8). When the arrow of the arm corresponds to the wished angle, the handle A6 is screwed again (FIG. 6) by stopping the arm A2.

[0015] In order to correctly sharpen the right teeth, the arm A2 must be located in the angle corresponding to the upper cutting angle (FIG. 4) of the tooth, but always on the right part (looking towards the front of the machine) (FIG. 9).

[0016] The chain stop A10 is situated on the left side of the operator and it stops the back of the tooth (FIG. 11). In this position the grinding wheel will sharpen all the series of the right teeth always by touching first the external part and by leaving any burr and impurity on the inner side only.

[0017] On the contrary, to correctly sharpen the left teeth Ñ according to the invention, it is possible to act as follows. The rear handle A6 is unscrewed and the arm A2 is released. The arm A2 is rotated and located on the same angle, but in the symmetrically opposite part (for example if it was in the angle 60° on the right, it should move up to 60° on the left side) (FIG. 12). The arm is fixed by clamping the handle A6. After this operation the angle of the vice is changed: the lower handle A8 is unscrewed releasing the vice A3 (FIG. 13).

[0018] The vice is rotated and located in an angle identical but opposite to that one used to sharpen the right teeth. If, at first, it was for example of 30° on the right (this angle corresponds to the upper sharpening angle as called by the saw manufacturers, FIG. 4), the vice must be rotated and fixed at 30° on the left (FIG. 13). It is possible to read this angle on the proper graduated scale A9 situated on the front part of the arm. This rotation must be done for every kind of electrical sharpening machine when a series of teeth is sharpened before passing to another one. At this point the saw is removed from the housing between the two yaws and it is rotated of 180° so that the side, which before was the external one (turned towards the operator), now is the inner side. The saw is inserted again between the yaws A1. Now it is necessary to correctly place again the chain stop on the rear part of the tooth. In order to allow this movement of the connecting rod A11 (in all the other sharpening machines it is not movable, but it is fixed on the left side of the vice) it has been provided on a pivot A12 and kept on stress on the vice body A3 by a spring A13 (FIG. 14). This spring allows the correct, total and fast displacement of the connecting rod A11 from the right side to the left side, in a specular way with respect to the original position. In addition, it allows the clamping to the vice body so that the connecting rod and the chain stop cannot displace from the wished position easily.

[0019] The left tooth is moved up to the chain stop A10 (FIG. 14), without any adjusting, it is now possible to sharpen this series of teeth too and, as shown, the grinding wheel (keeping its rotation in the direction opposite to the operator, that is anti-clockwise direction) will do the sharpening, also in this case, by touching first the external part and successively the inner part of the tooth (FIG. 5 drawing 2). For the above mentioned reasons, the external cuttings of all the series of left teeth will be perfectly sharpened, as well as it previously happened for the teeth of the right series.

[0020] b) To solve the point 3, the down movement has been used (towards the chain tooth located between the yaws A1); this movement must be necessarily carried out by the head of the machine A2 when the saw has to be sharpened. Electrical sharpening machines can be found in the market in which the clamping of the yaws and the consequent stopping of the saw are reached by the operator who must manually act on a lever (for every tooth to be sharpened it is necessary to turn the lever to close the yaws before the sharpening, at the end of the sharpening the opposite rotation is required to release it before the progress of the saw up to the following tooth). Some other electrical sharpening machines exist presenting or a hydraulic system (by means of an oleo piston fixed on one hand to the base and on the other hand to the upper part of the machine) or a piston pneumatically acted; both systems clamping the saw in the vice. The system according to the invention works in a completely different way.

[0021] By lowering the head A2 towards the saw and the vice body A3 the spring B10, which is fixed by supporting means to the head, is stressed. The spring acts on the lever B11 lifting its end as shown on the right side of the drawing (FIG. 1). A movement is, therefore, transmitted to the shaped block B12 rotating around a pivot B14 and consequently the protruding part B13 generates a pressure on the inner yaw causing the clamping of the saw when the tooth is sharpened. Said pressure is higher only when the grinding wheel scrapes off the tooth. By lifting the head again (FIG. 15), the stress on the spring B10 is weakened and the lever B11 and the shaped block B12 come back to the original position. The saw is, therefore, released again. It will be possible to get the progress of the saw between the two yaws up to the following tooth to be sharpened.

[0022] In other words, it is possible to say as follows:

[0023] The sharpening machine for chain saw according to the present invention comprises a rotating grinding wheel connected to an electric motor; by lowering the upper movable arm A2, by means of a mechanical transmission system formed by a spring B10 fixed to the arm and a lever B11 connected to the spring, it is possible to transmit a down movement to a shaped block B12 generating a pressure on the inner yaw of the vice body by rotating around a pivot B14; said pressure holds the saw fixed during the sharpening time; by lifting again the head the pressure on the spring B10 decreases, the block B12 and consequently the yaw come back to the original position and the saw is released again; at this point the operator can manually let the saw progress up to the following tooth to be sharpened.

[0024] The upper part A2, the motor and the grinding wheel as well are fixed to, can rotate both to the right and to the left of the base A4 with respect to the right angle 90° (center of gravity of the base); said rotation is so wide (40° towards the right and 40° towards the left) that it is possible to reach both the right and the left side of the angle corresponding to the upper cutting angle as called by the manufacturers of chain saws.

[0025] The down movement takes place on a groove A5 provided in the lower part of the machine A4 fixed to a support before the using as for example to a working desk; by means of a handle A6 fixed to a movable pivot in the groove, it is possible to fix the arm A2 in all the intermediate positions comprised between 40° (corresponding to the angle 50° of the graduate scale) on the right and 40° (corresponding to the angle 50°) on the left with respect to the center of gravity (right angle) of the base.

[0026] The connecting rod A11 to which the chain stop A10 is fixed, is balanced around a pivot A12.

[0027] A spring is fixed to the balanced connecting rod A11 and to the vice body A13; the stress clamping the connecting rod to the vice body is hold when it is either on the right or on the left side of the machine. 

1. Sharpening machine for chain saw, comprising a rotating grinding wheel connected to an electric motor; by lowering the upper movable arm, by means of a mechanical transmission system formed by a spring fixed to the arm and a lever connected to the spring, it is possible to transmit a down movement to a shaped block generating a pressure on the inner yaw of the vice body by rotating around a pivot; said pressure holds the saw fixed during the sharpening time; by lifting again the head the pressure on the spring decreases, the block and consequently the yaw come back to the original position and the saw is released again; at this point the operator can manually let the saw progress up to the following tooth to be sharpened.
 2. Electrical sharpening machine as in claim 1, wherein the upper part, the motor and the grinding wheel as well are fixed to, can rotate both to the right and to the left of the base with respect to the right angle 90° (center of gravity of the base); said rotation is so wide (40° towards the right and 40° towards the left) that it is possible to reach both the right and the left side of the angle corresponding to the upper cutting angle as called by the manufacturers of chain saws.
 3. Electrical sharpening machine as in claims 1, 2 wherein the down movement takes place on a groove provided in the lower part of the machine fixed to a support before the using as for example to a working desk; by means of a handle fixed to a movable pivot in the groove, it is possible to fix the arm in all the intermediate positions comprised between 40° (corresponding to the angle 50° of the graduate scale) on the right and 40° (corresponding to the angle 50°) on the left with respect to the center of gravity (right angle) of the base.
 4. Electrical sharpening machine as in claim 1, wherein the connecting rod to which the chain stop is fixed, is balanced around a pivot.
 5. Electrical sharpening machine as in claim 4, wherein a spring is fixed to the balanced connecting rod and to the vice body; the stress clamping the connecting rod to the vice body is hold when it is either on the right or on the left side of the machine. 